Electroplating



pril 30, 1946- E. w. RIEGER ET AL ELECTROPLATING Filed May 20 1945 3 Sheets-Sheet l Snnentors ERA/E51- W P/EGEI? c: J. KLEIN April 30,

E. W. RIEGER ET AL ELECTROPLATING Filed May 20. 1945 3 Sheets-Sheet 2 3nventors ERNEST W P/EsER CLARE (E J. KLEIN (Ittorn 5 PriBBOE, 4 E. w. RIEGER ET AL ELECTROPLATING s Shets-Sheet 5 Filed May 20, 1943 Snventors fR/ /E'ST ,Q/EGEQ CLARE cEJ KLEIN Patented Apr. 30, 1946 Ernest W. Rieger, Bloomingdale, Ohio, and Clarence J. Klein, Mai-land Heights, W. Va.,

poration oi Delaware assignors to National Steel Corporation, a cor- Application May 20, 1943, Serial No. 487,758 (Cl. 2o4 2os) 7 Claims.

The present invention relates to continuous electroplating of a moving strip having a conductive face. More particularly, the present invention relates to the continuous electroplatin of /strip metal such as steel with a coating metal such as tin, zinc, nickel, chromium, etc.

The continuous electroplating of strip material I has been developed along several lines. Some systems plate both sides of the strip at the same time while others plate only one side, subsequently plating the other if desired. Still baths and circulating electrolytic solutions have been used. One of the problems associated with continuous electroplating has been the maintenance or replenishing of the anodes. The anodes are formed of the metal being plated and of course being soluble become eroded by the metal of the anode replacing the coating metal in the electrolytic solution. As the anodes erode their surfaces become further removed from the face of the strip being plated. This necessitates changes in the electrical circuit to maintain a desired plating current. If this action continues, undesirable effects are introduced. Eventually the anodes become eroded to such extent that they must be replaced. If an entire anode replacement i carried out in one operation the electroplating action must be discontinued during the operation. I

The present invention provides an improved aparatus for continuously replacing the anodes and is a further development of the old idea of forming the anode of a series of anode elements. Fresh anode elements are introduced at one side of the anode and eroded anodes are withdrawn at the other side. Objectionable features of previous systems of this type have been removed by the present invention and an improved method and apparatus developed.

An important object of the present invention is the provision of an apparatus for continuously electroplating moving metal strip having a conductive face in which the soluble anode is replenished in such a manner as to result in improved electroplating action and improved practical operating features.

A further important object of the present invention is the provision of an improved apparatus for continuously electroplating moving strip having a conductive surface on the under side of the strip which is plated while the strip moves in a horizontal plane.

A further important object of the present invention is the provision of an apparatus for continuously electroplating moving strip having a conductive face in which all of a series of anodes may be replenishedfrom the same side of the path of the strip resulting in improved practical operating features.

A further important object of the present invention is the provision of apparatus for continuuously electroplating moving strip having a conductive face in which aeration of the electrolyte is reduced to a minimum.

These and other objects and advantages will be apparent from the following description and accompanying drawings which disclose a preferred embodiment of the present invention.

Figure 1 is a plan view with the strip removed of an electroplating cell incorporating the present invention;

Fi ure 2 is a view in cross section taken on the line 2-2 of Figure 1;

Figure 3 is a view taken in cross section on the line 3-3 of Figure 1; 0

Figure 4 is a plan view with the strip removed of an anode arrangement similar to that of Figure 1 constituting another embodiment of the present invention; and

Figure 5 is a view in cross section similar to Figure 2 showing a further embodiment of the present invention.

In electroplating lines of the type in .which the preferred embodiment of the present invention is applicable a continuously moving metal strip which has been previously cleaned and pickled is passed through a series of electrolytic baths or a long electrolytic bath in which soluble anodes incorporating the coating material are disposed on one side of the moving strip. In one form the horizontally disposed strip moves along in contact with the surface of the bath, the electrolytic solution being circulated against the lower face. Where both sides of the strip are to be plated the moving strip metal is then reversed and passed through a similar section in which the other face is opposed to the anodes. For plant simplicity and labor saving reasons it is sometimes preferred that each line have an operating side from which all normal operating actions and adjustments are made. Since the electroplating portion of the line normally includes identical cell structure, whether with separate baths or one elongated bath, the present disclosure is confined to one cell and asso; ciated structure.

Referring to Figures 1, 2 and 3, reference numeral 9 indicates a strip being treated and i0 indicates generally a tray having a pairof partitions H and I2 defining a pair of overflow troughs l3 and IE and an electroplating cell l5 which is filled with an electrolyte (not shown) with which strip 9 makes contact. In operating position in the line, tray I is positioned with troughs I3 and I4 disposed on either side or the moving strip.-'Trough I! is on what may be termed the operating side or the line and for this reason a bracket member I8 is arranged along the outer wall of the tray on this side to act as an abutment member in the use of an anode moving jack. Such a. jack forms no part or the present invention and will not be described herein. Transversely to the direction of movement or the strip, cell i is divided by an anode guide and electrical contact member indicated generally at 11. Member I 1 includes a guide It forming a pair of shoulders l9 and on a contact member 2| which in turn is supported on current carrying member 22 which presents an upstanding portion 23 having bus bar connections 2 protruding therefrom. Extending parallel to member II are a pair of guide members 25 and 28. Shoulders l9 and 2c of member l1 and the upper surfaces of guide members 25 and 26 are inclined upwardly in a parallel plane from the operating side of the cell for purposes later to be described. The soluble anode elements have their ends resting on shoulders I! and 20 and guide members 2| and 28. One series or anode elements form an anode indicated generally at 21 supported at one edge by guide member 25 and the other series of anode elements form an anode indicated generally at 28 with an edge resting on guide member 26.

Openings 2!! and 30 are provided for the introduction of circulating electrolytic solution into cell l5. Each of the. anode elements of a series is separated from the adjacent anode element so as to form spaces through which the solution can circulate. The liquid level of the solution in cell I5 is defined by the height of the walls thereof, there being no other exit the solution overflows them. That solution overflowing partition walls H and I2 collects in troughs" and M while that overflowing end walls ii and 32 of the cell collects in pans 33. Solution spilling into the troughs eventually will flnd its way into a pan 33 through outlet openings 34 and It. Solution in each pan 33 is withdrawn through collecting opening 36 for treatment and recirculation.

Since many electrolytic solutions are subject to objectionable oxidation by contact with air the solution circulating system is to reduce turbulence and the resulting entrainment of air. Openings 34 and are connected with downcomers 31, the exit ends or which are preferably below the liquid level of the solution (not shown) anode elements to take care of situations where the width of the circulating stream of electrolytic solution is to be narrower. Thus where a narrower strip is being plated some of the anode elements can be omitted and the blocks when moved into the positions shown in dotted lines in Figure 2 will confine the stream of circulating solution to a path more nearly the dimensions of the anode.

All the metal parts of the apparatus except the anod elements which are subject to contact with the electrolytic solution are covered with rubber or some suitable covering which will not react with the chemicals in the solution. Contact member 2|, which forms no part of the present invention, is formed of a nonmetallic substance which will conduct electricity and is not acted upon by the electrolytic solution.

With the anode elements in the position shown in Figure 1, i. e., with their length extending substantially parallel to the path of the strip, the spaces between the anodes may cause a streaked deposit. Where this feature becomes objectionable the arrangement of anode elementsshown in Figure 4 i utilized. In this case each of the anode elements is turned with its length at an angle to the path ofthe strip such that the entire face of the strip passes over substantially the same amount of anode. In other words each point across the face of the strip passes over the same amount of anode element and space between the anode element. It may be mentioned that an exception can be made adjacent the edges l of the strip where local eflects' sometimes give in pan 33. The size of openings It and I! is so desi ned that the overflow from cell II will normally be taken care of while maintaining a body of electrolyte in the troughs. Riser pipes 38 and 39 are provided to take care or excess overflow when necessary. These riser pipes are connected to downcomers Ill similar to downcomers 31. In order to maintain the circulation of electrolytic solution confined to a path including the anodes a pair of blocks II and 42 are inserted on either side of each inlet opening it. These blocks close all the spaces between member I! and members 25 and 26 so the stream of electrolytic solution is directed up through the spaces between the anode elements. In cross section each block ti and 42 is triangular. the triangles being similar. By forming the blocks so that each or the three legs of these triangles is a different predetermined length it is possible to use each block in three different positions along the under heavier plating. Thus with the anode elements in the position shown in Figure 4 and the strip of awidth like that shown in Figure 2 it will be apparent that the edges or the strip would not pass over the same amount or anode element as the interior portions of the face. In efiect the current density at the edges would nevertheless remain uniform with that of the rest of the strip. Obviously, any other angular arrangement or the anode elements than that shown in Figure 4 may be used to accomplish the desired results.

Considering each anode specifically, it will be seen that it is mad up of a series of anode elements identical with those making up any other anode. For this reason only one series of anode elements need be described. Referring again to figuresLzandiLanode nismadeup ofa series of anode element starting with anode element 43 at the lower end of the inclined plane presented by shoulder I 9 and guide member 25 and ending with anode 44 at the upper end of the inclined plane. A representative intermediate anode along the inclined plane is indicated at 45. The shape and relation of each anode element in the series will best be understood from a description of the operation. Considering the line in continuous operation, a fresh anode elemept corresponding to anodeelement I3 is insertedin the position shown. In order to get anode element it into this position the remainder of the anode elements are moved up the inclined plane so that the one previously occupying the position indicated at It is ejected from electrolytic relation with the strip and can be withdrawn from the bath. A fresh anode element is inserted at 43 each time the previously introduced anode element, and conseq tly all the anode elements, has been subjected to a predetermined amount 01 erosion due to the electroplating action. It will be apparent that each anode element as it side of the 15 is moved up the inclined plane by the introducascents fected. Thus-due to the narrowing of the anode elements by erosion the spaces between' them become wider. Additionally, the top surfaces of the anodes become rounded, changing the effective height of the anode element with respect to the cathode or strip face. All these factors contribute to a reduction of the effective anode surface toward the upper end of the inclined plane. In the present invention therefore the angle the in-' clined plane makes with the face of the strip is designed not only to take care of the diiference-in height or thickness of the electrodes due to erosion but also to bring the anode elements toward the upper end of the inclined plane nearer to the face of the strip. Since an appreciable proportion of the resistance in the plating current circuit exists between the anode and the strip, by varying the distance between the anode and the face of the strip across the anode, a very nice control of current density across the face of the strip can be attained. Thus'the angle of the inclined plane is so adjusted that the anode elements are brought closer to the strip as they approach the position 44 an amount such that the average current density over the anode, measured at the face of the strip and across the path of the same, is substantially uniform. Although there is less effective anod area at anode element it, the distance to' the. cathode being lessfected by moving all the anode elements a distance equal to the width of a fresh anode element. This allows the maintenance of a. predetermined relationship between the side edge of the anode and the side edges of the strip to control the amount of plating action at the edge of the strip. In this type of operation the erosion of the anode between movements will result in t a bet een th ode an the fac of the he Sp ce w e an d e face. With careful design it will be apparent that strip becoming greater. This increases the resistance of the circuit and causes a reduction in current density which must be compensated for either by increasing the applied voltage or reducing the speed of the strip. The entire anode sup- Phases since where desired the lack of uniformity of current density across the face of the strip may be compensated for by other means and in such cases would not be an objectionable feature. Additionally, the inclined surface need not be a straight line, such configuration of the anode support being used to compensate for inequalities in anode to strip spacing.

Referring to Figure 5 an anode supporting arrangement is shown in which the angle at which the anode elements approach the strip is changed during their travel across the path of the same. Under some conditions the anode supporting. arrangement shown in Figure 2 would result during continuous operation in a greater spacing between anode-elements and the strip at the eroded side of the anode than at the side where the fresh anode element is introduced. This would occur despite the fact that substantially uniform current density existed across the face of the strip at the anode when operation started. The fact that the plating action would be the same across the anode might under some conditions result in a more rapid reduction in height of the anode elements at the eroded side of the anode due to the fact that loss ofthe same amount of metal from the eroded anodes as from the fresher anodes would decrease the cross section of the former in greater proportion. The continuation of this action would result in a gradual decrease in average current density on the eroded side of the anode due to the gradual greater proportional port may be moved to maintain the spacingbetween the face of the anode and the face of the strip substantially the same. Shims 59 (see Figure 3) are shown for this purpose. In an alternate method of operation the anode elements are the remaining anode elements.

increase in spacing on this side. The present invention contemplates compensation for this phenomenon when so desired. The anode support in Figure 5 is shown as having two straight line sections although any number of sections could be utilized, even up to giving a curved configuration where necessary. The section indicated at 68 in this specific embodiment is of a length such that three anode elements are supported thereon. The section indicated at 50 supports V Thus where replacement of the anode is effected by moving the anode elements the space of one fresh anode element, the anode element corresponding to that shown at 45 will move from section 69 on to section 50 and line contact between the support and the anode element .will be maintained. The anode support of Figure 5 will for all practical purposes give an anode with a plane face opposed to the strip face. Obviously, the more sections used in the anode support the more closely the surface of theanode will approach the plane surinvention each fresh anode element 43 is given a specific shape to achieve best results. As will be more readily seen in Figures 1 and 3, spacing members $6 for maintaining anode elements spaced are preferably formed integral with each anode element on one side thereof. The opposite side of each anode element is formed in a straight line and by making the anode element wider between spacing elements 46 than outside, of them, wider spacing is achieved adjacent. the ends ofthe anode elements so that the circulating solution will be directed toward the ends of the anode elements. The top surface adjacent each end of an anode element is beveled off at 41 to compensate for eddy currents and reduced circulation of the solution at these points. All the above features of'the structure of the anode elements result in an area of substantially uniform plating action across the face of the strip.

In starting up an electroplating line incorporating the present invention, a series of anode elements forming each anode are cast in the shapes herein shown.v

The term uniform current density" as used herein means an over-all current density for an anode such that substantially equal plating action results at all points across the face of the strip over the time period each such point is in electrolytic relation with the anode.

We claim:

1. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed tray presenting an electroplating cell having electrolyte therein and adapted to have the strip move across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell presenting an inclined surface submerged in the electrolyte extending across the path of the strip for movably receiving a series of anode elements, inlet means for introducing electrolyte into the cell at a point in the path of the strip, and partition blocks extending along the path of the strip on each side of the inlet, the partition blocks having cross sectional shapes in the form of similar triangles with unequal legs, the legs being of such lengths that when each is used as the base of the triangle, the height of the triangle will correspond to that of a point on the inclined surface.

2. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed tray presenting an electroplating cell having electrolyte therein and adapted to have the strip move across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell presentingan in;-

clined surface submerged in the electrolyte extending across the path of the strip for movably receiving anode elements, and a partition block in the cell extending along an edge of the strip, the partition block having a cross sectional shape in the form of a triangle with unequal legs, the legs being of such lengths than when each is used as the base of the triangle, the height of the triangle will correspond to that of a point on the inclined surface.

3. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed electroplating cell having electrolyte therein and adapted to have the strip move in a horizontal plane across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell below the plane-of the strip presenting a surface inclined with respect to the horizontal extending across the cell laterally to the direction of movement of the stri and submerged in the electrolyte, the inclined surface being formed of electrically conducting material and adapted to be connected to a source of electroplating current, a plurality of elongated anode elements in contiguous relationship to one another movably supported on the inclined surface, the anode elements extending in the direction of movement of the strip, each anode element having a bottom surface in electrical contact with the inclined surface and a top surface,

the top surfaces lying in a common plane adja- 16 cent the underside of the strip and presenting an area having a width substantially corresponding to the width ofsaid face.

4. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed electroplating cell having electrolyte therein and adapted to have the strip move in a horizontal plane across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell below the plane of the strip presenting a surface inclined with I respect to the horizontal extending across the cell laterally to the direction of movement of the strip and submerged in the electrolyte, the inclined surface being formed of electrically conducting material and adapted to be connected to a source of electroplating current, a plurality of elongated anode elements in contiguous relationship to one another movably supported on the inclined surface, the anode elements extending in the direction of movement of the strip, butnat an angle thereto such that an intermediate point on the face passes over and in diagonal relation to an anode element during said movement of the strip, each anode element having a bottom surface in electrical contact with the inclined surface and a top surface, the top surfaces lying in a common plane adjacent the underside of the strip and presenting an area having a width substantially corresponding to the width of said face.

5. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed electroplating cell having electrolyte therein and adapted to have the strip move in a horizontal plane across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell below the plane of the strip presenting a plurality of surfaces similarly inclined with respect to the horizontal extending across the cell laterally to the direction of movement of the strip and submerged in electrolyte, the inclined surfaces being formed of electrically conducting material and adapted to be connected to a source of electroplating current, a plurality of anodes in the cell each including a group of elongated anode elements in contiguous relationship to one another movably supported on an inclined surface, the anode elements extending in the direction of movement of the strip, but at an angle thereto such that an intermediate point on the face passes over and in diagonal relation to an anode element during said movement of the strip, the anode elements of one group being arranged at an angle to the anode elements of another group, each anode element having a bottom surface in electrical contact with an inclined surface and a top surface, the top surfaces lying in a common plane adjacent the underside of the strip and presenting an area having a width substantially corresponding .to the width of said face.

6. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed electroplating cell having electrolyte therein and adapted to have the stripv move in a horizontal plane across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell below the plane of the strip presenting a surface inclined with respect to the horizontal extending across the cell laterally to the direction of movement of the strip and submerged in the electrolyte, the inclined surface being formed of electrically conducting material and adapted to be connected to a source of electroplating current, a plurality of elongated anode elements in contiguous relationship to one another movably supported on the inclined surface, the anode elements extending in the direction of movement of the strip, each anode element having a bottom surface in electrical contact with the inclined surface and a top surface, the top surfaces lying in a common plane adjacent the underside of the strip and presenting an area having a width substantially corresponding to the width of said face, the plane being inclined toward the face in the direction of the inclined surface to a degree such as to maintain substantially uniform current density across the face.

'7. Apparatus for continuously electroplating a moving strip of material having a conductive face comprising a horizontally disposed electroplating cell having electrolyte therein and adapted to have the strip move in a horizontal plane across the cell from end to end with the face thereof in contact with electrolyte in the cell, an anode supporting structure in the cell below th plane of the strip presenting a surface inclined with respect to the horizontal extending across the cell laterally to the direction of movement of the strip and submerged in the electrolyte, the inclined surface being formed of electrically conducting material and adapted to be connected to a source of electroplating current, the angle the inclined surface 1 makes with the horizontal increasing across the cell in the direction in which the inclined surface approaches the face, a plurality of elongated anode elements in contiguous-relationship to one another movably supported on the inclined surface, the anode elements extending in the direction of movement of the strip, each anode element having a bottom surface in electrical contact with the inclined surface and a top surface, the top surfaces lying in a common plane adjacent the underside of the strip and presenting an area having a width substantially corresponding to the width of said face, the plane being inclined toward the face in the direction of the inclined surface to a degree such as to maintain-substantially uniform current density across the face.

ERNEST- W. RIEGER. CLARENCE J. KLEIN. 

